This invention relates to a process for producing frozen fruits, and more particularly to a process for producing frozen avocados which will not easily disintegrate or discolor on and after thawing.
Since it is difficult to maintain the quality of avocados for a long period of time, they must be consumed in a relatively short period of time after being harvested. That is one of the primary reasons why avocados are expensive in the market. In order to solve this problem, many methods have been proposed for preservation of avocados so far.
As a general method for preservation of fruits and vegetables, quick ultra-low temperature freezing is widely used. This preservation method can be successfully applied to those products such as broccoli, carrots and the like and they are sold on the market as frozen foods. However, it is difficult to apply such a quick ultra-low temperature freezing method to those high-water content products such as tomatoes, oranges or watermelons and the like because they disintegrate upon thawing (defrosting).
Avocados, although not as much as watermelons or tomatoes, contain relatively a large amount of water and are delicate to outside stimulation. Therefore, when ultra-low temperature freezing is conducted to avocados, they are easily disintegrated upon thawing. In addition, the surface of the frozen avocados is discolored upon thawing or defrosting owing to oxidization of the surface of the avocados. Because of these problems, avocados are not widely used as frozen foods today.
In order to solve these problems, dehydration of avocados by heat drying prior to freezing is proposed. Such dehydration can be conducted by means of a hot air or microwave treatment. These methods can be effectively applied to avocados for the purpose of maintaining the shape of frozen avocados upon thawing. However, employing such a method requires another facility and additional expense for that purpose. In addition, because the water content and size of each avocado varies widely, it is difficult to uniformly dehydrate all of the avocados to an appropriate degree by these methods.
With respect to the problem of discoloration on and after thawing, anti-browning agent such as citric acid has been used. However, in order to prevent the discoloration by such an anti-browning agent, a substantial amount of such agent must be used, resulting in further cost increase in producing frozen avocados.
Further, in order to successfully produce the frozen avocados, the taste of avocados should not be impaired by the freezing process.
Therefore, it is an object of the present invention to provide a process for producing frozen avocados which do not disintegrate upon thawing in a simple and economical manner.
It is another object of the present invention to provide a method for producing frozen avocados which do not discolor on and after thawing.
It is a further object of the present invention to provide a method for producing avocados which can maintain the original good taste.
Further object of the present invention is to provide a method for producing frozen avocados capable of performing the continuous processing for freezing including cutting, boiling, cooling, drying, quick ultra-low temperature freezing in a successive and economically efficient manner.
The present invention is a process for producing frozen avocados which can achieve the above objects effectively, comprising the steps of;
cutting avocados into a plurality of pieces and removing seeds from the body of each of the avocado pieces;
heating the avocado pieces in a steam container by introducing steam thereto;
removing the avocado pieces from the steam container; and
freezing the avocado pieces by a quick ultra-low temperature freezer.
Preferably, the avocado pieces removed from the steam container are subsequently cooled in ice water and dried for a certain period of time prior to the ultra-low temperature freezing.
More preferably, prior to the drying, the skin of the avocado pieces is removed.
More preferably, a certain amount of baking powder is added to the hot water in order to maintain the clear color of avocado pieces after freezing.
More preferably, a certain amount of vinegar or salt is added to the hot water in order to prevent the oxidization of the avocado pieces on and after thawing.
More preferably, a certain amount of sugar, Japanese sake or wine is added to the hot water in order to maintain the taste of the avocado pieces in good condition.
According to the present invention, since avocado pieces are heated by the steam in a large container, the water content of the avocado pieces is uniformly dehydrated through the heating process in a very easy and economically efficient manner without using any additional facility for that purpose.
Further, according to the present invention, since the avocado pieces are uniformly dehydrated through the process of heating and drying prior to the ultra-low temperature freezing, disintegration of the avocado pieces upon thawing is prevented.
Further, according to the preferred embodiment of the present invention, since avocado pieces are cooled in the ice water after heating but prior to ultra-low temperature freezing, the discoloration of the avocado pieces after thawing can be effectively prevented.
Further, according to the preferred embodiment of the present invention, since baking powder is added to the avocado pieces before heating by the steam, dehydration of avocado pieces is promoted and the clear color of the avocado pieces is maintained.
Further, according to the preferred embodiment of the present invention, since anti-oxidization agent such as vinegar or salt is added to the avocado pieces through the heating process, the anti-oxidization agent is effectively applied to the avocado pieces so that the discoloration of the avocado pieces after thawing can be effectively prevented without using any additional facility or independent process for that purpose.
Further, according to the preferred embodiment of the present invention, since wine, Japanese sake or sugar is added to the avocado pieces, the bitter taste of avocado pieces after thawing can be removed without using any facility or process for that purpose.